【leetcode】1380. Lucky number in matrix

subject ：

1380.  The lucky number in the matrix 
 To give you one  m * n  Matrix , The number in the matrix   Each are not identical  . Please press   arbitrarily   Return all the lucky numbers in the matrix in order .
 Lucky number refers to the elements in the matrix that meet the following two conditions at the same time ：
 The smallest of all elements in the same row 
 The largest of all elements in the same column 
 
 Example  1：

 Input ：matrix = [[3,7,8],[9,11,13],[15,16,17]]
 Output ：[15]
 explain ：15  Is the only lucky number , Because it is the smallest value in its row , It is also the maximum value in the column .
 Example  2：

 Input ：matrix = [[1,10,4,2],[9,3,8,7],[15,16,17,12]]
 Output ：[12]
 explain ：12  Is the only lucky number , Because it is the smallest value in its row , It is also the maximum value in the column .
 Example  3：

 Input ：matrix = [[7,8],[1,2]]
 Output ：[7]
 
 Tips ：

m == mat.length
n == mat[i].length
1 <= n, m <= 50
1 <= matrix[i][j] <= 10^5
 All elements in the matrix are different 

violence :

class Solution {
    
    public List<Integer> luckyNumbers (int[][] matrix) {
    
        int m = matrix.length;
        int n = matrix[0].length;
        List<Integer> list = new ArrayList<>();
        for(int i = 0; i < m;i++){
    
            int resMin = Integer.MAX_VALUE;
            int idx = 0;
            // Traverse each element of the current line to find the minimum value 
            for(int j = 0; j < n;j++){
    
                resMin = Math.min(resMin,matrix[i][j]);			
                // Assign the coordinates of the minimum value of the current row to idx
                if(resMin == matrix[i][j])idx = j;
            }
            int resMax = Integer.MIN_VALUE;
            // Traverse the current page i The smallest element of the row idx Column by column traversal 
            for(int j = 0; j < m;j++){
    
            	// Roll variables to record 
                resMax = Math.max(resMax,matrix[j][idx]);
            }
			// If this value is the minimum value of the current row   again idx The maximum value of the column   Then he is the lucky number   Add it to the result 
            if(resMax == resMin) list.add(resMin);
        }   
        return list;
    }
}